From 31241d57508735c23ce88019ada33e00580aa99e Mon Sep 17 00:00:00 2001 From: Emil Tantilov Date: Thu, 21 Nov 2024 20:40:59 -0800 Subject: [PATCH] idpf: add read memory barrier when checking descriptor done bit BugLink: https://bugs.launchpad.net/bugs/2111953 [ Upstream commit 396f0165672c6a74d7379027d344b83b5f05948c ] Add read memory barrier to ensure the order of operations when accessing control queue descriptors. Specifically, we want to avoid cases where loads can be reordered: 1. Load #1 is dispatched to read descriptor flags. 2. Load #2 is dispatched to read some other field from the descriptor. 3. Load #2 completes, accessing memory/cache at a point in time when the DD flag is zero. 4. NIC DMA overwrites the descriptor, now the DD flag is one. 5. Any fields loaded before step 4 are now inconsistent with the actual descriptor state. Add read memory barrier between steps 1 and 2, so that load #2 is not executed until load #1 has completed. Fixes: 8077c727561a ("idpf: add controlq init and reset checks") Reviewed-by: Przemek Kitszel Reviewed-by: Sridhar Samudrala Suggested-by: Lance Richardson Signed-off-by: Emil Tantilov Tested-by: Krishneil Singh Signed-off-by: Tony Nguyen Signed-off-by: Sasha Levin Signed-off-by: Manuel Diewald Signed-off-by: Mehmet Basaran --- drivers/net/ethernet/intel/idpf/idpf_controlq.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/net/ethernet/intel/idpf/idpf_controlq.c b/drivers/net/ethernet/intel/idpf/idpf_controlq.c index c7f43d2fcd13..559746e9029c 100644 --- a/drivers/net/ethernet/intel/idpf/idpf_controlq.c +++ b/drivers/net/ethernet/intel/idpf/idpf_controlq.c @@ -376,6 +376,9 @@ int idpf_ctlq_clean_sq(struct idpf_ctlq_info *cq, u16 *clean_count, if (!(le16_to_cpu(desc->flags) & IDPF_CTLQ_FLAG_DD)) break; + /* Ensure no other fields are read until DD flag is checked */ + dma_rmb(); + /* strip off FW internal code */ desc_err = le16_to_cpu(desc->ret_val) & 0xff; @@ -566,6 +569,9 @@ int idpf_ctlq_recv(struct idpf_ctlq_info *cq, u16 *num_q_msg, if (!(flags & IDPF_CTLQ_FLAG_DD)) break; + /* Ensure no other fields are read until DD flag is checked */ + dma_rmb(); + q_msg[i].vmvf_type = (flags & (IDPF_CTLQ_FLAG_FTYPE_VM | IDPF_CTLQ_FLAG_FTYPE_PF)) >>